Valve seat grinding machine



Feb- 5, 1935* F. o. ALBERTsoN 1,989,905

v 4 VALVE SEAT GRINDING MACHINE Y v Filed Feb. 19, 1954 5 Sheets-Sheet 1 f y I 106 103 H6'. 12272245- Feb. 5, 1935. ALBERTSON l 1,989,905

VALVE SEAT GRINDING MACHINE Filed Feb. 19, 1954 Z5 Sheets-Sheet 3 Mew gg fzzs jeflaofav M bwwmgkadu Patented Feb. 5,- 1935 y;

UNITED PATENT 'OFFICE `vALvE sEA'r GRINDING`1inicn11-rnv-y n Fransf/O. Albertsoni Sioux City, Iowafassignor to V v --Albertson & Company, lncgfSioixir-Cityg l* 'incorporation o'flowa Y v Application Feiilfuaxyis, 1954',lseiafNai'nLs o j 1s olainis. (citi-241)'v The present invention `relates` to valve seat ed to produce a'finishedvalveY seat of predetergrinding machines particularly adapted forv use mined angularityandf adapted toifeliminate the in. the forming, reconstruction or repair rof valve 1 hand-lapping operation whichzwas found necesseats of linternal combustion engines.' However', sary with grindingfmachine's of theipriorr art.

r the methods and apparatus are `of general applica'- Another object .of the invention isthe provision x5 tionl and may be utilized for valves of different o'f 'ang improved grindingtoolofthe full seat conkinds and for other grinding operations, and I do tact type which is adapted to eliminate the clognot Wish to be limited to the particular use-of my ging loading'xof-sthe' grinding wheel or the inventiondisclosed therein. Y grooving of. th`e.seat,- and ltolfprovidl-i 'a `grinding l." Valve 'grinding machines of theprior art may "tool, whichisrselfcleanin'g., 10 be classied into machines ofthe full contact'type Anothrzobjectfofthe'invention is vthe rprovision inwhich the stone is-in contact withthe working 'of an improved grinding wheel adapted' to dissurface to be` ground throughout; the' 'entire perse the cuttings continuously and to prevent periphery ofhthe stone, and'single contact -maloading' of :the .wheelorlling with the cuttings tacts only one side of the'valve, or the stone-may of 'the wheel at zthesurface,y the cuttings being disbe arranged eccentrically with respect to the axis persed by acurrent of air, 'and 'centrifugal force,

of revolution. 1 L I at the periphery of the wheelvwhen the wheel is The devices of the prior arthave, howevenbeen Alifted periodically from' the "seat,

Very complicated, requiring either a complicated Another object .of the invention is the provision 20 mechanism forrotating and revolving the stone, of an"v improvedmethod'and apparatus whichV is or requiringI a4 ball bearing tool. holder for supadapted to disperse the cuttingsV by means of a porting the stone, and thedevices of the prior art vibratory movement-oi' vthestone either ina verhave not been able to grind the valves with a suittical direction on the" pilot or angularly in a 2,5 able finish. 'L i The'difiiculty with the` full seat contact "grindpilot, so as yto preventloading of 'thewheel and ing wheels of the prior art was that this resulted groovingof the seat "and vto produce a finished surin clogging or loading of the wheel with the cutface on'thevali'fe."V i tngs or material ground yfromthe seat, andthis Another object Vof the inventionv is the' provi'- caused a change in the contour of the stoneand "sion of f animproved tool assembly, including a '30 resulted in the grooving of the valve seat. All the motor driver 'and afuniversal connection between devices o'f-the prior `art were Aalso very expensive thefmotcr driver and the' grinding wheel,v includ- `on account of the complicated mechanism `re ing` means Afor eleminating detrimental shocks quired and on account of the apparent :necessity on the grinding wheel, but adapted to produce a for using anti-friction bearings, and such devices dualaction of grinding and dispersion of the cut- -35 could not -be'brought within the means `of the tings by meansof a single 'grinding wheel` located ordinary garage owners, who could not afford exfor full contact vwith the seat. pensive mechanism and make a profit on the work Other objects andadvantages ofv thev invention to be done.t will be' apparent from th'effollowing description 40 One `of the objects of the present invention is and from tlieaccompanying drawings, in which "40 the provisionof an improved method of reconsimilar characters of' reference-indicate"similar structing or grinding valve seats, .by means of partsthrou'ghoutthe several views. which the extremely hardseats "of `stellite,vtung Referring to the drawings; stensteel, orother hardened alloys canbe ground 1 is a side elevationalfview 'of' the grindquickly and uniformly to produce a finished seat, ing apparatus with avalvefstem' and valve stem with a` minimum amount of labor.. Y guide in vertical section `on a planepassing The tendency in the construction of valve' seats through theaxis of the guide', the assembly inf for internal combustion enginesis toward the use cluding' the motor driver, tool holder, grinding of seats of 'harder material, and it is one of the wheel and pilot;

chines in which the stone is so tilted. that itfcon'- of the 'intersticesbetween the abrasive particles 15 lateral direction by ,means ofthe flexibility of the 25 objects of the invention tol'provide an' .improved Fig. 2 is a vertical Asectional view, taken on a 50 apparatus which is capable :of working such hard plane. passing through the 'axis of the pilot, with seats more satisfactorily than could be done with the tool holder and grinding wheel in section, and the vdevices of; the prior art.; the pilot' in elevation Y Another object of the invention is to provide an Fig. :3 is a fragmentary enlarged sectional view improved method and apparatus which is adaptof the connectionbetween the .motor driver` and y55 u Fig. 5 is a transverse sectional view talren ,onV

the plane of the line 5--5 of Fig. 4, showing the structure of one of the springs for're'silientlyI sup`V porting the drive shaft for axial movement; i

Fig. 6 is another sectionalview takengonfthe plane of the line 6--6 of Fig. 4 through thenon-` circular driving portion of the shaft and its socket in the tool holder;

Fig. 7 is another sectional view showing .theltool holder spring in plan, the section being taken on the plane oftheline 7-7 of. Fig. 4, looking in the direction of the-arrows;

Fig. 8 is an elevational view of a-.modifie-d grinder assembly, in which -the samepilot and :tool holder are.r` employed, with' a iiexiblerdriveI shaft,

and the ordinarydrill motor; having a` :suitable clutch; i i

Fig. 9 is a side elevational viewofv the flexible shaft employedinthe deviceofFigJ 8 Referring to Fig. 1,-1the-com`pleteassembly-of the grinding apparatus peferablyiincludes fthe motor driver 20, a tool holder V21, a grinding wheel 22, and a pilot stem-23.A l. v 1 l 'f The apparatus is illustratedinconnection with a valve seat consisting` cfay hardened metalring 24, which has been fixedlysecured inthe block 25 o-f an internal `combustion engine having -a valve seat guide 26. z

'I'he pilot 23 is preferably `of the type having 'a lower cylindrical part27 which fits the substantially cylindrical part of the valve stem guide 26 very closely, within cnethousandth of an inch, for the purpose of centering thepilot 23 in the guide and locating itaxially of the' guide.

'I'he pilot isV also preferably provided with va. very gradually tapered portionI 28 which extends down into the upper part of the valve sternguide 26 and may be fixedly wedged intheV guide by merely shoving the ,pilot downward.- The taper is preferably about twenty-three thousandths of an inch per foot, and constitutes the sole means .of securing, but any suitable taper may beused which will effect the wedging action and secure the pilot,` l

Another typey of pilot which maybe usedis the expanding pilot'shown in my prior Patent No. 1,902,207, issued March 21, 1933.

Referringto Fig. 4, the electric motor driver 20 is shown inY detail in this figure. The motor vdriver preferably lconsists'of an electric motor of enlargement 36 causes the fan 34 to rotateiwith the armature shaft 33. The armature shaft 33v is -preferablysupported at both of its ends by self- ,aligningball bearings consisting of .the races 38,

39 and the balls 40 suitably mounted in a metal casing 41 located in a bore 42 in the end of the casing of the motor.

The bore 42 may be located in a metal partition 43, forming a part of the motor housing 20, and the end of the motor housing may be closed by the gear housing 44 which fits against the partition43.- Suitable slots 145, between the partition 43 and `thef-gmain: part'ofl 4the moto;` housing 29 provide for the outward flow of the air caused by the fan 34.

The motor shaft preferably supports at its lowerend' a drive gear or pinion 46, which is adapted,..to, drive the vdriven gear 47, which is ,rriounted on a drive shaft 48. Drive shaft 48 has its upper end supported by anti-friction bearings comprising the outer race 49, balls 50, and inner frase 51.- 1

`The Imember 52 comprises a cup leather for preventing the outward flow of the lubricant from the anti-frictionbearings 49, 50, and 51 into the fan chamber.: TheA upperl end 'of the shaft 48 is slidably received in the inner race 5l, and the shaft is'rotatably and slidably supported bynmeans of. a; lower anti-friction bearingcom.- prising the -outer race x53, balls' 54, `and inner race55. I

A spacingv` collar 56 is located between theV gear 47 and inner race 55 on the shaft 48; A suitable `oi1 seal orA plate 57i-is located at. the upper -side of the races 53, 55, the latter race fitting linto the Aaperture in plate 57, andv the' outer race 53: being spun over the -outer edge of plate 57. The outer race 53 is preferably: slidably mountedin a metal sleeve 58 having an inwardly extending annular flange 59 at the top. 'A metal Awasher plate (50A is'located'in the sleeve 58 and trally' locatedaperture 62, the aperture. 62 be- -ing bordered by. aplurality of .resilient metal `tongues 63 formed by slitting the metal outward f radiallyy at 64 Iand making an arcuate cut at 65. In one embodiment of my invention-threey of the spring'tongues 63 are provided, their upper vsides engaging thewasher. plate 60. VThe lower sideof' Washerspring.v 61 rengages the top of the race 53, and the Washer springlriscompressed between the racex53 and ther platev 60,l thereby resilientlyA urging the race 53 and with it balls 54, outer race 55, and shaft 48, .in a downward direction. y

`When axial force is impressed upon `the .shaft 48 in an upward direction, the springv washer .61 gives sufficiently to permit the shaft to move upward into the motor. Furthermore, the spring 61 serves asa spring` support for the weight of thexnotor and removes from the grinding wheel the shock `which would, otherwisebe caused by the weight ofthe motor on the shaft 48..v The amount of unsprung weight bearing upon Vthe .grindingI wheel isgreatly diminished by resilibexcaused in case Athe motor were not ysprung vor resilientlv supported withl respect tothe shaft 48.. E. I

The sleeve 58 may have a drive tjina bore 66 in the lower end of the gear housing 44. Sleeve 58 is preferably threaded at its lower inner end "i '675 so vas f to receive the oil seal` housing which vention consists of a hateshaped leather having l a cylindrical portion 70 anda radially outwardrlhe cylindrical portion the "enlarged cylindrical-portion 72 of ther shaft 'by means of a coiled garter spring 73;" A channel-shaped metal member 74, having inwardly extending'annularfflanges houses the spring 73 -andholds it'into'engagement with the leather 70.

The lower end fof shaft 48isprovided with a threaded 1portion'75 for receiving the internally threaded driving knuckle 76wh ich has a 'threaded bore 77. f vAt its lowerfend the driving knuckle l76 is provided: with va-nofiecirczular portion 78 -which may, for example, be hexagonal in form,

and which'hasa flat -lower end '79.r`

' The fiat end 79 is preferably beveled orv chamf- Vfered atthe `cor-ners 80 for-'fthepurpose 4of removingthesharp edges which would otherwise wear, so 'that the' physicalcharacteristics of the end ofthe driving knuckle-will'remain the same.

The driving knuckle 76 is-' preferab1y made of special steel, and its action `on the tool holder vwillbe described in-detail hereinafter. The motor driver 20 preferably operates vat a speed Within therange Vof 13,000 RfP. M.,` which is considerably in excessof the speeds previously used by the drivers'ofthe prior art, and the mechanism is capable of operationat this high speed without the necessity for anti-friction bearings in the' toolholder on account of the fact that there is no bearing load onthe bearings of the tool 'holder except that which is involved by its vguiding function.

- The tool holder Zlpreferably comprises a substantially cylindrical housing sleeve 81, which Y A handle, and which maybe constructed of tubular fiber, Bakelite,v or other suitable material'. The housing 81 is supported by meansof a supporting body or sleeve 82 vof substantially cylindrical outer form, and vprovided with a radially outwardly extending flange 83 at its lower end adapted to l,be flush with the outer surface of the housing 81'.' Flange 83 is provided with an annular shoulder 84 adapted to receive the sleeve orV housing 81, and the supporting sleeve 82 is provided with a downwardly extending tubular portion 85, which is externally threaded for the purpose of receiving the threaded hub'86 of the grinding wheel.

The vgrinding wheel 22 comprises a suitable grinding stone of carborundurn, emery, or other suitable material which is secured lto the tubular hub 86 by means of cement 87. On its upper surface the grinding stone 22 `has a cardboard annulus 88 cemented thereto, bearing the data Aregarding the size andangularity of the grinding stone. The upper surface 89 of the grinding stone is at, and the periphery 90 is cylindrical.v The bottom 91 is preferably flat, and the working surface 92 is accurately frusto-conioal in the case of valves for internal combustion engines, being dressed to frusto-conical form by Ameans ofthe improved dressing tool described in acompanion application, ySerial No.y 711,847, filed February 19, 1934. 'Y

The threads 75 of threads on the sleeve 85 and hub 86 ofthe grinding wheel are, ofcourse, opposite in direction to the direction of rotation of these partsso that the drive shaft 48' and the 'the driving knuckle 76 and-thegrinding wheel 22 will Aboth be driven homeontheir threaded supports by the action of the driving of the grinder. l' r The supporting sleeve 82 is provided witha cylindrical Vbore 93 extending throughout the major portion of the sleeve, andwith an enlarged counterbore 94 at the top. The counterbore 94 is threaded at its upper end 95 for receiving Athe end of `plug 96,Which hasa reducedthreaded end 97 threadedinto the bore'95. End plug 96 has an outwardly extending' annular shoulder 98 which-=engages the v'end vof sleeve 82 when it is threaded home therein, and it is also preferably provided with the cylindrical surface 99 and annular shoulderlOO, the former being received iny the housing 8l', and the: latter abutting against the end of the housing 81 -for supporting the upper end of housing'Sl on sleeve 82. Pins 101 driven throug-hthe housing-'81 into bores 102 in thev reduced portion`-j97 of plug 96 firmly secure all of these parts together and prevent the ,threaded parts from becoming loose.

rality'vof radially 'extendingl rib'formations 108,

which in this case are located on two diameters at right angles to each other, for the purpose of further stiffening the spring, but in some embodiments of the'invention'the spring might be made o f sufficient stiffness Without the ribs 108.

The ribs 108 preferably extend downward when the springwasher 106 is assembled with the toolV holder 21 soas ftofincrease-the bearing surface against which the end of the driving knuckle 76x, engages over the surface Awhich it would engage if the ribs projected upward. 'I'he spring washer'A 106 rests against an annular shoulder 109 at/the base ofthe counterbore 104 andr is clamped in placeby a threaded member 110, the end of which engagesthe upper surface of the spring adjacent its periphery.

Threaded member '110`-has its periphery threaded to be received in the threaded bore 104. andA italso, has its threads extending in such a direction that it will be 'driven home by the driving action of the motor driver. i The threaded member 110 is provided with la centrally located aperture 111 which ispreferablynon-circular in form and slightly 'larger than the' end 78 of the driving` knuckle 76 so as"A to permit the driving knuckle to tilt inthe non-circular or hexagonal aperture 111, as yshown in'Fig'. 2.

The clearance is more clearlyillustrated in Fig. 6 and in Fig. 3,-i-and v'the action and purpose of this structure'will Afurther be described in detail. f Y

The present tool holder presents a radical departure from the practices 'of the prior `art with respect to bearings or tool holders in respect to the materials employed. It has heretoforebeen customary to employ one hard metal and one soft metal in the two complementary parts of a trunnion 'and a bearing, 'on account of the lesser degree of wear which is broughtabout by the action of the hard metal on the soft metal. Inl motor grinders of this type, however, the relatively soft metal, such as bronze or brass `bearing metal, takes up the emery particles or carborundum particles or grindings, which become embedded in the soft metal, and this speedily wears down the other hard metal and renders the tool inaccurate.

In the present invention the upper endf22` o f pilot 23 is preferably made of hardened steel, and the bore 93 of the supporting sleeve 82 is provided with a bearing sleeve 113, having an accurate cylindrical bore p 114, and the bearing sleeve 113 is also preferably made of hardened steel.

Bearing sleeve 113 may be a" drive flt in the supporting sleeve 82, and it should fit the upper end of the pilot with a slight clearance sufficient to permit it to rotate freely, but with suflicient accuracy to prevent any wabbling .or other movement. f I

It is found that when a slight 'amount of.lubri' cant is used on these two hard contacting surfaces the device may be driven at veryv high speeds, such as, for example, 13,000 R. P. `M., without appreciable wear, as neither of the hard surfaces takes up the grinding wheel particles in the manner that took place in the soft bearing metals of the prior art. The pilotrand bore 93 are tted accurately by a'lapping operation.y

Therefore, the tool holder` may be used for a long period of time and retains its accuracy and fit with respect to the pilot, and it is not necessary to utilize anti-friction bearings which involve other moving parts, but the present device can be made far more accurate, due to the fact that it uses two complementary cylindrical parts which may be accurately ground to proper size and fit.

Referring now to Fig. 4, it will be evident that the drive shaft 48 may be moved inward and outward with respect to the motor 20 by virtue of the sliding arrangement of its bearings in their sockets and the resilient action of the spring 61 which urges the shaft outward. This spring action eliminates shocks on the grinding wheel which might otherwise be caused by the unsprung weight of the motor, and the spring 106 in the tool holder has a similar action in preventing such heavy shock to the grinding wheel that the grinding wheel would break.

Referring to Fig. 1, this is a side elevational view of the assembly with the driver in the middle or vertical position, which the driver generally assumes when the 'operator begins his operations. While the driver is operating at a high speed, however, the operator sways the handle 115 back and forth through a relatively small distance, moving the driving motor 20 angularly with respect to its driving knuckle '76 as a center. This swinging movement of the motor results in a different action on the grinding Wheel 22, and effects a dispersion of the cuttings and constant cleaning of the grinding wheel, as follows. v

Referring to Fig. 3, it will be observed that the non-circular or hexagonal end 78 of the driving knuckle is there shown at an angle with the end plug 96 or at an angle to the axis of the pilot 23 and tool holder 21. As the hexagonal part 78 rotates there is an axial movement of this hexagonal part, due to the distance between the spring 106 and the successive corners 116, 117, 118, and 119 of the hexagonal part. In other Words, at the instant shown the corner 116 of the driving knuckle 78 is in engagement with the spring 106, but as the corner 118 rotates downward toward the position where it will engage the spring 106 there is an axial movement of the drive shaft downward which is equal to the distance X shown in Fig. 3. Thus the use of a non-circular driving member disposed at an angle causes the drive shaft tofgive a number of downward impulses toi the tool holder, the shock of which is, however, partially absorbed by the spring 106, and the shock of the motor weight is not transmitted to the tool holder on account of the fact that the motor is spring supported by means of the spring 61 This vertical impulse action of the drive shaft on `the tool holder produces variations in pressure on the grinding wheel 22 as it grinds the seat 24. Furthermore, the pilot stem 23 is a relatively slender and resilient metal member, and the tilt of the drive shaft 48 and driving knuckle 76 gives these periodic impulses a lateral component which tends to cause the tool holder to vibrate with .the pilot stem in a lateral direction, somewhat-like the vibration of a tuning fork. Thus the tool holder is subjected to vertical impulses and/or vibrations and to lateral impulses and/or vibrations, and the grinding wheel is subjected to variations in vertical pressure and variations in angular movement about the lower end of the pilot as a center, which permits the grinding wheel to lift slightly from its working surface and disperse the cuttings.

The exact theory on which the action is based cannot be certainly determined, but it is positively known that the swaying action of the motor driver with the structure of the pilot, tool holder and shock absorbing springs as described results in a complete dispersion of the cuttings while the grinder is operating, and the grinder is capable of producing a substantially mirror-like valve surface without any grooves or other irregularities and without producing any noticeable wear on the grinding stone. All of this may be done at a very high speed, the high speed aiding the smooth action of the grinder and subjecting the grinder to high frequency vibration, as well as inlreasing the speed at which the work may be one.

Assuming a rotary speed of 13,000 R. P. M., using a hexagonal driving knuckle, each corner of the grinding knuckle will produce one complete vertical oscillation or variation in pressure or lateral oscillation on the pilot because the impulse which is given to the tool holder by the corners ofthe hexagonal driving knuckle takes place between the flat portion of the driving knuckle and each corner. The frequency of vibration would, therefore, be six times 13,000, or in the range of 78,000 complete vibrations per minute.

, Referring to Fig. 8, this is a modified assembly for the purpose of illustrating the fact that the 'present tool holder may be employed with an ordinary drill motor. The assembly here includes the same pilotand tool holder 21 as set up in Fig. 1, but the ordinary drill motor 120, which is provided withla chuck 121, is connected to the tool holder 2l by means of flexible shaft 122, having at its lower end a driving knuckle end 78 of the same shape as previously described.

Inthis case the drill motor operates at about 2,000 R. P. M., and the work is accomplished much more slowly and in a different manner, due to the differentstructure of the assembly, but the present tool holder is shown to be capable of use with ordinary drill motors as well, which places these tools Within the means of a large number of users whc'scannot'afford to buy la 4special motor driver'for the'grinder. It should also be pointed out that the grinder is preferably supplied with la'rough or 'coarse stone gularity of the valve seat in question.' The valvev stem pilot is then iixedly secured in the valve stem guide by shoving the tapered portion of the pilot down into the guide until the pilot is fixed therein. The tool holder bearing the grinding stone. is then slidably and rotatably mounted onv the guide, and the motor driver is held above with itsdriving knuckle, having the non-circular end in the non-circular. socket ofthe tool'holder.

It is not necessary to .exert any pressure on the motor driver, but, on the contrary, a very light pressure is desirable, such as-.that exerted by the weight of the motor itself. The motor may then be turned on and the grinding stone `and tool holder? rotated at a high speed of approximately 13,000 R. P. M., While the handleof` the motor is oscillated back and forth through a small arc scribed as rotating a grinding stone'inr full-'con-l tact with a valve seat, without subjecting the.

grinding stone to periodic vibrationsvarying the pressure and/or area of contact of the stone by.y

angular oscillations of the stone in such'manner as to vconstantly disperse the cuttings, and prevent clogginglor loadingl of the stone.

It will thus be observedl that I have invented an improved valve seat grinder, the structure jof which is considerably simplified overthe devices of the prior art, inasmuch as it does not require.

any complicated driving mechanism for both-rotating and revolving the stone, and yet the de- Vvice effects a dispersion of the cuttings, constant. cleaning of the stone, and produces a mirror-likeY finish on the valve seat, which could notbe done withthe full contact stones of the prior art.

The spring action. of the resilientlymounted driveshaft prevents shocks to the stone by means of the mass of the motor and the periodic im;

pulses transmitted to the tool holder and stone" by means of the resiliently mounted drive shaft produces a vibratory action ofthe stone, which slightly lifts the stone from its seat periodicallyv as the grinding progresses and permits the cuttings-to be thrown off centrifugally, this action.v

being also aided by the air currents causedby the vrotating stone.

The presentL grinding apparatus is so simple that it may be manufactured at a much lower cost than the complicated devices of the prior art, particularly the eccentric type of grinders, and this grinder may be manufactured at a cost which is'within the me'ans of a vast number of purchasers.:

While Ihave`A illustrated a preferred embodiment. of my invention, many modifications may be made without departing from the spirit of the invention, and-I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope ofthe appended claims. Having thus described my invention, what I claim is new and desireto secure by Letters Patent of the United States, is:

1. In'avalveseat grinder,r the combination of a valve stem. pilot with a tool holder yadapted to be slidably and'rotatably mounted on said pilot and a grinding'wheel carried by said tool holder, a driving: shaft for said tool holder, driving means for said shaft, a universal connection between said tool holder and said driving shaft, and a spring interposed between said driving shaft and said tool holder comprising a substantially fiat and resilient metal memberv supported at its'outer edge and located'in a socket in the end of lsaid tool. holder.

2. In a valve seat grinding apparatus, the cornbinationof apilot stem'adapted to be centered with respect to a valve stem guide, a tool holder slidably and rotatably mounted on said pilot stem, agrinding wheel mountedto rotate with said tool holder, a motor driver,.noncircular complementary parts onsaid motor driver and tool holder whereby the tool holder is driven by said motor driver, resilient meansinterposed between said motor driver and tool holder, said non-circular parts having suitable clearance whereby the motor driver may be tilted and the non-circular parts on the motor caused to transmit periodic impulses tothe tool holder for the purpose of dispersing the cuttings.

.3. -In a valve seat grinding apparatus, the combination ofa pilot stem adapted to be centered with respect to. a valve stem guide, a tool holder slidably and rotatably mounted on said pilot stem, agrinding wheel mounted to rotate with said tool holder, a motor driver, non-circular tool; holder whereby'the tool holder is driven by said motor driver, said non-circular parts having suitableclearance whereby the motor driver may be-tilted and the non-circular parts on the motor caused totransmitperiodic impulses to the tool holderforl the purpose of dispersing the cuttings, and resilient: means interposed between the motor and the tool holder for absorbing the direct shocks .of. said. impulses on the grinding Wheel. r 4. In a valve seat grinding apparatus, the combination of .a pilot stem adapted to be centered with respect to afvalve stem guide, a tool holder.

slidably and rotatably mounted on said pilot stem, a'grinding wheelmounted to rotate with said tool holder, a motor driver, non-circular complementary-parts on said motor driver and tool holder whereby the tool holder is driven by said motor driver, resilient means interposed between said motor driver andtoclholder, said non-circular parts having suitable clearance whereby the motor driver maybe tilted and the non-circular parts `on the' motor caused to transmit periodic impulses to the tool holder for the purpose of dispersing` the cuttings, said motor having its drive complementary parts on said motor driver and shaftrresiliently -mounted .for axial Vmovement whereby the Weight of the motor is spring mounted with respect to the grinding wheel.

5. In a tool holder for valve seat grinding apparatus, the combination of a supporting sleeve provided with an outwardly projecting 'ange adjacent one end, a threaded extension beyond said flange, a cylindrical part on the other side of said ange for engaging a handle sleeve, a threaded plug mounted in the opposite end of said supporting sleeve and having a cylindrical surface for engaging in said handle sleeve, said plug having an outer cylindrical surface ush with the cylindrical surface of said handle sleeve and means for securing said plug to said supporting sleeve to retain said assembly in permanent assembly.

6. In a tool holder for valve seat grinding apparatus, the combination of a supporting sleeve provided with an outwardly projecting flange adjacent one end, a threadedextension beyond said flange, a cylindrical parton the other side of said flange for engaging a handle sleeve, a threaded plug mounted in the opposite end of said supporting sleeve and having a cylindricalr surface for engaging in said handle sleeve, said plug having an outer cylindrical surface ush with the cylindrical surface of said handle sleeve, said end plug being formedwith' a non-circular socket, and a spring located in said non-circular socket and adapted to engage the end of a non-circular drive shaft for driving said tool holder to absorb the shocks caused by said non-circular drive shaft.r

7. In a valve seat grin-der, `the combination of a valve stem pilot with a tool holder slidably and rotatably mounted on saidpilot, said tool holder having a non-circular socket, a drive-shaft having a complementary non-circular part adapted to be received in said socket, resilient means mounted in the base of said socket for engaging said drive shaft, said socket having sufhcient clearance so that the drive shaft may be tilted therein and the successive corners of the Vdrive shaft may transmit axial impulses to the tool holder as the drive shaft rotates in tilted position.A

8. In a valve seat grinder, the combination of a valve stem pilot with a toolholder slidably and rotatably mounted on said pilot, said tool holder having a non-circular socket, a drive shaft having a complementary non-circular part adapted to be received in said socket, resilient means mounted in the basev of said socket for'engaging said drive shaft, said socket having sufcient clearance so that the drive shaft maybe tilted therein and the successive corners of the drivev shaft may.

transmit axial impulses to the` tool holder as the drive shaft rotatesin tiltedposition, said pilot being resilient, whereby the horizontal component of the impulses transmitted to the tool holder by said tilted drive shaft causes. lateral vibration of the tool holder and pilot to effect a dispersion of the cuttings.

9. In an apparatus for grinding `valveseats, the combination of a pilot stem adapted to be centered with respect'to a valve lstein guide, a tool holder slidably and rotatably mounted on said pilot stem, a grinding wheel mounted to rotate with said tool holder, resilient means carried by said tool holder in a socket-.for receiving a drive shaft, a motor driver comprising a motor having a field and an armature shaft, an armature and a drive pinion, a separate drive shaftl protruding from said motor vdriver and engaging in said socket against said resilient means, said separate drive shaft having a gear for engaging said pinion and being slidably mounted with respect to saidjmotor, andresilient means for urging said 'separatedrive shaft outward with respect to the motor whereby the said separate drive shaft may oscillate with respect to the motor and transmit vibrations to a tool holder without vibrating the motor.

f 10. In an apparatus for grinding valve seats, the combination of a pilot stem adapted to be centered with respect to a valve stem guide, a tool holder slidably and rotatably mounted on said pilot stem, a grinding wheel mounted to rotate with said ltool holder, resilient means carried by said tool holder in a socket for receiving a drive shaft, a motor driver comprising a motor having a field and an armature shaft, an arma-y ture anda drive pinion, a separate drive shaft protruding from said motor driver and engaging in said socket against said resilient means, said separate drive shaft having a gear for engaging said pinion and being slidably mounted with respect to said motor, and resilient means for urginglsaid separate drive shaft outward with respect to the motor whereby the said separate drive shaft may oscillate with respect to the motor and transmit vibrations to a tool holder without vibrating the motor said separate shaft being'rotatably mounted in anti-friction bearings and said anti-friction bearings being arranged to permit reciprocation of the drive shaft with respecty to the motor. i

11. In a tool holder for valve seat grinders, the combination of a tubular metal member having an internal bore adapted to t upon a valve stem pilot, said tubular metal member having a threaded end for receiving a threaded hub of a grinding wheel, and having a non-circular socket formed at its opposite end, and a spring comprising a resilient flat metal member having its outer edge secured to said 'tubular metal member in said socket and adapted at its central portion to engage a non-circular driving member when inserted in said socket.

12. Ina driver for valve 'seat grinders, the combination of a motor provided with a casing, al

gear casing carried by one end of said motor casing, said motor h'avingan armature with a shaft projecting into said'gear casing, a pinion on saidA armature shaft, a drive shaft. projecting from said, gear casing and having a non-circular drive shaft, saiddrive shaftr having a gear engaging saidv pinion, bearings for said drive shaft in said' gear housing .permitting the sliding move-` ment of said driveA shaft in the direction of its axis, and resilient'means in said gear casing for urging said shaft outward whereby the motor driver is vadapted to be resiliently supported by saidspring when' resting on a driven member by meansgof said drive shaft.

13.l The method of dressing valve seats of internal combustion engines which comprises rotating a grinding wheel in substantially full contact with a valve seat, simultaneously subjecting the grinding wheeifto periodic vibratory impulses in the direction toward Athe valve seat and subjecting the grindingwheel to lateral components of impulses tending alternate-ly to lift one or the other'side of the grinding Wheel and to depress the opposite side of the grinding wheel to cause the grinding wheel to lift sufiiciently from the seat to disperse the grindings.

FRANS o, ALBERTsoN. 

